1. Field of the Invention
The invention relates to an improved sterilizing tunnel for pharmaceutical containers.
2. Description of the Prior Art
One sterilizing tunnel of the type with which this invention is concerned is known from DE 198 46 277 C2. Sterilizing tunnels of this kind, which are used in the pharmaceutical industry, particularly for sterilizing ampules, vials, or the like, have ventilating fans in the individual zones along which the containers are conveyed, which produce an air flow that circulates around the containers in a laminar fashion from top toward the bottom. Depending on the zone, the circulated air is scrubbed by means of clean air filters (so-called HEPA filters) disposed above the containers and is heated and cooled by means of heating and cooling units. Due to the flow direction of the air, the heating and cooling of the containers occurs from the direction of the container mouth toward the container bottom, i.e. unevenly over the height of the container, which can damage the containers or produce stress cracks in them, particularly in relatively thin containers or when a container has walls of different thicknesses.
It is also known to coat the containers with emulsion-like substances (e.g. silicone) before entry into the sterilizing tunnel. In this case, the sterilizing tunnel is also used for fixing and baking the substance into the surface of the containers. In the sterilizing tunnels of the prior art in which hot air is circulated through filters, the filters can become clogged with baking residues of the substances, consequently reducing the service life of these filters.
There are also known sterilizing tunnels whose heating units are operated solely by means of radiant heat generators (e.g. infrared radiators).